A powerful message sent this week by the US and Britain to the leadership of the rebel so-called Free Syrian Army (FSA) won’t change much on the battlefield in the run-up to the “Geneva II” peace conference scheduled for next month, but the political damage to the mainstream opposition group is considerable.

International mediator Lakhdar Brahimi has given Syria’s warring sides until Dec. 27 to name their delegations to Geneva II, officials said Thursday.

More than 30 ministers from big powers, regional countries and others are due to gather in the resort of Montreux on Jan. 22 to give their blessing to the negotiations between the government of President Bashar Assad and militants fighting to oust him, according to Daily Star newspaper.

Brahimi is scheduled to broker the first face-to-face Syrian talks beginning the following day. Iran and Saudi Arabia are among those slated to attend, diplomats said. The conference is designed to follow through on the Geneva I meeting, which endorsed the establishment of a transitional authority with full executive powers, part of a political process to end nearly three years of fighting that has killed more than 120,000 people and displaced millions.

Syria’s fractured opposition now has two weeks to name its delegation members as its military wing grappled with Wednesday’s decision by Washington and London to suspend shipments of non-lethal aid to the militants via Turkey.

The decision was announced several days after FSA warehouses and headquarters near the Turkish border were seized by extremist militants from a coalition of seven major terrorist groups.

The FSA’s leadership dismissed as “nonsense” reports that its head, Gen. Salim Idriss, was forced to flee to Qatar as a result of the dispute. Its spokesmen said Idriss was busy meeting with leaders from the coalition called “Islamic Front” near the border, in a bid to sort out the issue of the warehouses.

Both the FSA and the Islamic Front have portrayed the developments as a misunderstanding – they say the FSA asked for the Front’s help to defend the facilities from an attack by hardline militants from the Islamic State of Iraq and Greater Syria (ISIS).

Commenting on the decision, US Defense Secretary Chuck Hagel said that “what has occurred here in the last couple of days is a clear reflection on how complicated and dangerous this situation is and how unpredictable it is.”

“We continue to support General Idriss and the moderate opposition,” he said at a Pentagon news conference.

“But this is a problem ... and we’re going to have to work through it and manage through it with Gen. Idriss and the moderate opposition.”

The incident highlighted how Idriss’ SMC was unable to maintain control of its own bases and it coincides with recent statements by Hagel and other senior American officials that Washington is engaged in seeking out moderate, extremist rebel groups in a bid to get them involved in the political process to be launched by Geneva II.

The SMC has failed to forge a coherent rebel force to counter either the Islamic Front or the hardline militants of ISIS and the al-Nusra Front, although this dynamic has been in play for some time, according to analysts who spoke to The Daily Star.

The decision to suspend even nonlethal aid to the SMC also underscores a policy of going all-out to move the Syrian crisis into the realm of politics and away from the battlefield, where officials fear the rising influence of the hardline rebel groups.

Yezid Sayigh, of the Carnegie Middle East Center in Beirut, said the decision by Washington and London “isn’t a hugely significant move militarily – but it is more significant politically, and will undermine the sense among some Syrians that the SMC is relevant.”

The SMC, Sayigh said, has been on a “downward slope” ever since its founding last year.

“It has never exercised effective command and control, and never been particularly effective,” he said, other than in creating a framework for limited coordination among rebels in isolated military engagements. Sayigh expressed skepticism about Idriss’ supposed flight to Qatar, but said it would be instructive to monitor whether the FSA leader would be able to set foot inside Syria after the warehouse debacle.

Idriss and other FSA commanders, meanwhile, have repeatedly criticized a lack of sufficient support from outside backers, including Western countries.

The suspension of non-lethal military assistance nonetheless undercuts any “military option” that Washington can bring to Geneva, according to Joshua Landis, a Syria expert based in the US.

“Most people understood the lack of control by Idriss, but an important pretense has now been pulled away,” Landis said. “ Washington can go to Geneva, but it doesn’t have the military option.”

A number of difficult decisions and challenges now await the rebels’ backers, Landis said.

American officials recently stated that they are engaging with extremist rebel groups to get them to accept a political process, but these groups have categorically rejected Geneva II.

Landis said that with no feasible military strategy, Washington should be expected to go all-out to convince international players to halt assistance to the warring sides on both sides of the conflict.

For now, Moscow and Tehran are fully supportive of their ally Assad remaining in power, while Persian Gulf countries don’t favor a political solution, Landis said.

“It will all depend on what kind of compromises can be worked out between Saudi Arabia and Iran, and between Russia and America” as part of Geneva II, Landis said.

Moreover, the Ahrar al-Sham militia, which is part of the Islamic Front, has recently been engaged in clashes and a power struggle with the hardline militants of ISIS, also in Aleppo province, which presents a complicated picture for policymakers.